Feeling like she couldn't talk to the MC about the Kindra situation strikes me as either an excuse or something deeply personal to her that she never actually said anything about.I don't believe she did anything out of vindictiveness or even rage. More likely, it has been selfishness. She realized her shortcomings and screwed over the MC for personal profit and advancement. Which is the same reason she keeps trying to screw him over and steal shit from him. If he reaches his full potential, she will become meaningless. She can't risk that.
The fact that she is still is attracted to the MC just makes her betrayals all the more egregious.
There are reasons for her behavior, but no justifications.
For the MC, it was just tuesday. By that logic, I get why she's enraged still. It doesn't mean she gets to pretend that was a justification, but I get it. Sometimes you can see something as sentimental and the other partner does not.